Tuning system



Jan. 9, 1940.

D.'R. DE TAR 2,186,823 TUNING SYSTEM Filed July 1, 1937 2 Sheets-Sheet 1 Inventor Donald R. DeTar,

H is Attorn egg- Jan. 9, 1940.

Inventor:

Donald F. DeTar,

is AttOY'TIH.

Patented Jan. 9, 1940 UNITED STATES PATENT OFFICE TUNING SYSTEM New York Application July 1, 1937, Serial No. 151,432

3 Claims.

My invention relates to automatic tuning systems for high frequency apparatus and more particularly to control means for such tuning systems. It has reference to that class of antomatic tuning systems which is commonly employed in radio receivers to eiiect tuning of the receiver to a desired frequency in response to a switching operation, as in response to the pressing of a button. Commonly in such systems a plurality of buttons, or control keys, are employed, each corresponding to a particular frequency and means are employed automatically to tune the receiver to the frequency corresponding to the particular control key operated.

One of the objects of my invention is to provide certain mechanical improvements in such systems whereby the control of the tuning system is facilitated and rendered more efficient.

Another object of my invention is to effect certain improvements in the driving means for the tuning device to facilitate manual tuning of the receiver, notwithstanding the drive connection between the motor and tuning device. One object of this improvement is to avoid drag of the motor when the tuning device is manually driven.

Certain other objects of my invention pertain to improved stopping means for the tuning device when the desired condition of resonance to to a desired frequency is attained, and to an improved assembly of keys for controlling the motor.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings in which Fig. 1 represents an embodiment of my invention, Figs. 2, 3 and 4 illustrate details, Fig. 5 indicates a modification and Fig. 6

a detail.

Referring to Fig. 1 of the drawings, I have shown at l therein a tuning device which may comprise the tuning condenser of an ordinary radio receiver. The shaft of this condenser is provided with a pulley 2 by means of which it 50; is driven. At 3 I have conventionally indicated a motor for driving the condenser I, this motor having a shaft 4 upon which is mounted a gear 5. This gear meshes with a second gear 6 which is mounted on the same shaft with a smaller gear 8, the latter of which meshes with the ring gear 9 of an epicyclic gearing system.

This system includes, in addition to the ring gear ially with the sun gear in, and being belted to 1 the pulley 2.

The construction of the epicyclic gearing sys-v tem is such that sufiicient friction exists between the gears 9, l0, and II so that these elements when driven by the motor through gear 8 re main stationary relative to each other, that is, the three gears rotate as a single unit about the axis of gear I0. Gear II and shaft l2 are thus carried about the axis of gear l0, thereby driving the pulley [4 at a speed determined by the ratio of the external diameter of ring gear 9 to the diameter of gear 8.

If it be desired to tune the receiver manually by rotation of knob 2!, the drag of the motor and friction in the gear chain between ring gear 9 and the motor is such that ring gear 9 remains stationary. Rotation of the knob and gear It, therefore, causes intermediate gear H to travel around the inner periphery of ring gear 9 and thus rotate pulley M at a much reduced speed.

In this way the motor may be driven by either the knob 2| or the motor 2, each operating freely and practically independently of the other and at the same time no shifting or transferring of gears is necessary, both the knob and the motor being continuously in driving'relation with the condenser.

While I have shown the various gears of toothed type, it will, of course, be understood that these may be of the friction type to reduce backlash etc., and that the various other mechanical expedients now known to the art to insure the smooth and free operation of the system may be employed.

The motor is controlled by an electrical control system comprising an assembly iii of push buttons, or control keys, of which live are shown in the drawings. Of course many other control keys may be incorporated in this assembly. Of these keys, keys l1 and I8 and any additional keys, not shown, which may be included correspond respectively to each of the different frequencies to which the receiver is to be tuned. The key I9 is one which is operated when it is desired to tune the receiver manually as by manipulation of the handle 2|. Key 20 is employed I to turn the receiver oil when it is not in use, and key 22 is employed for energization of the motor if desired during the manual tuning operation.

These keys are all mounted in a unitary assembly comprising parallel plates 23 and 24, each of which is slotted to receive the different keys. The keys are bifurcated at the inner ends thereof to receive springs 25, the inner ends of which engage the plate 23, these springs operating to bias the keys to the left as shown in the drawing, that is, to their normal position.

Key 22 is one which when released by the operator always returns to its normal position. The remaining keys when pressed by the operator remain in the operated position, being locked in that position by a locking member 26. This locking member comprises a plate which extends throughout the length of the key assembly, the outer edge being supported as at 2'! in small openings in the plate 24 and the inner edge being bent downwardly to engage in notches 23 in the upper edge of the different keys, plate 26 being biased downward against the keys by means of a spring 29. Key ii is shown in its operated positionand plate 26 is shown resting in the lefthand notch 28 of that key, thereby locking the key in that position. If now key I3 be pressed, as member 26 rides from one notch 28 of this key to the other, it is raised sufliciently to release key l'i. In this way the operation of any key except key 22 releases any other key which may be locked in its inner position.

At 3! I have shown a relay having an armature 'il-which operates a plurality of pairs of contacts 32, 33 and 34, these contacts being included in certain circuits of the motor and receiver later to be described. This armature is also provided with a projection 36 which when the armature is attracted lies in the path of movement of two wings 3? on the gear 5 of the reduction drive gear train, thereby preventing rotation of that gear when the relay 3i is energized. One side of this relay is connected to one side of a suitable source of operating potential 46 and the other side is connected to the plate 23 and thence through the receiver keys ll, 18 corresponding to the different frequencies and contacts 33, 39 cooperating therewith to the respective contacts 38', 39' of a commutator 23. This commutator comprises a substantially semi-circular plate 4| having a plurality of concentric slots 43, in which slots the different contacts 38, 39', etc. are mounted. Cooperating with these contacts is a movable contact 42 which is mounted within an insulating block Mt carried by an arm 45 which is mounted on the shaft of the tuning device.

Contact 52 is connected to one side of the source of potential 33 andto ground,if desired, through the arm :35. When this arm engages a stationary contact corresponding to a push button which has been pressed, a circuit is completed through relay 3!. With the apparatus in the position shown in the drawings, this circuit extends from one side of the source 46, through arm 25, movable contact 42, stationary contact 38',

conductor 53, contact 33 which is engaged by key ll, key ill, member 23, conductor 52, winding frequency control system of the receiver.

motor, this circuit extending from one side of the source 46 through contacts 32 of the relay, contacts 53 .of key 20, contacts 54 of key I9, and thence through motor 3 to the opposite side of source 45. At the same time contacts 33 of the relay interrupts the ground connection of the automatic frequency'control. bus of the receiver. This bus may, for example, comprise the conductorover which unidirectional potential-is supplied from the detector of the receiver to the means employed for controlling the frequency of the oscillator. Removal of this ground by contact 33 places the automatic frequency control device in normal operation. Bymeans of contacts 34 a ground connection is removed from the silent tuning conductor of the radio receiver. This conductor may extend, for example, to the grid of the first audio stage of the receiver thereby to silence the receiver when the conductor is grounded. By reason of these operations the receiver is in its normal operating condition.

Let us assume now that it be desired to tune the receiver to a frequency corresponding to the key l8. Key I3 is pressed inward, thereby, through locking device 26, releasing key H. Upon release of key ll, relay 3! is deenergized and its armature 33 moved out from engagement with wing 31, thereby permitting rotation of the gear 5. At the same time contacts 32, 33 and 34 are closed-contacts 32 completing the circuit of the motor, whereby the motor operates to drive the tuning condenser. Contacts 33 ground 'the automatic frequency control conductor and contacts 34 ground the silent tuning conductor, thus silencing the receiver during the tuning operation. When the arm 55 has been rotated until contact 52 engages stationary contact 39', relay 31 is again energized, which again stops the tuning condenser, deenergizes the'motor and, by reason of its contacts 33 and 34, restores the receiver to its normal operating condition.

In case the motor operates the condenser in such a direction that arm 45 moves away from contact 39', rather than toward it, then such movement continues to the limit of the range of movement of the condenser at which time reversing switch R is operated by one or the other of two arms r, mounted on the condenser shaft. This switch alters the energization of the motor and causes it to reverse its direction of rotation. Arm 45 then moves until engagement is made at contact 39 where the motor is deenergized.

ductor and thus permits normal response of the receiver. Its contacts 56 ground the automatic frequency control conductor through contacts 33 of the relay and thus disable the automatic The receiver may now be tuned manually by rotation of the knob 2!.

It will be observed, however. that the knob 2| is connected to the tuning condenser shaft through a drive system of considerable stepdown ratio. Accordingly if a large movement of the condenser be necessary to tune the receiver to a desired station by means of the knob 21, the operation may become laborious. In this case the operator may press button 22 which bears the n accordance with the slot in which the stationary:

legend motor. This button, by means of contacts 51, energizes the motor, which drives the tuning condenser. When the tuning condenser has reached the position where the receiver is tuned approximately to the frequency desired, as may be noted by the position of the index (not shown) upon the dial of the receiver, the operator may then release the motor button and complete the tuning operation manually by rotation of knob 2|. As previously stated, motor key 22 is not locked in its inner position, but immediately returns to theposition shown under its bias when released by theoperator.

When it is desired to turn the receiver off, the operator presses the off button 2!) which, by means of its contacts 58, deenergizes the receiver and, by means of its contacts 53 opens the motor circuit. The receiver may now, again, be turned on by pressing the manual button or any of the frequency selecting buttons l1, 48, etc.

I It will be observed that the rotation of the condenser is stopped by movement of projection 35 of the relay armature in the path of movement of wings 31 of the gear 5 thereby practically instantly stopping the condenser. The drive ratio between gear 5 and the tuning condenser shaft is, of course, high, with the result that the tuning device is stopped accurately in the desired position. The small movement of the gear 5 after energization of relay 3| is not sufficient to operate the condenser sufficiently to affect the accuracy of tuning to any appreciable degree. Were no other means provided, however, the entire inertia of the motor armature would be expended upon the relay armature, thus subjecting it to stress which might necessitate its heavier construction than would otherwise be necessary. To avoid such heavy construction of the relay 3!, a friction clutch is included between the gear 5 and the motor shaft. The construction of this clutch is best shown in Fig. 2, in which the shaft of the motor is indicated at 4. Upon this shaft are mounted two collars and GI, between which is mounted the gear 5, having the wings 31 and a spring 63, the spring pressing the gear 5 against the collar 60. Accordingly, when rotation of the gear 5 is stopped by movement of the armature 36 between wings 31, shaft 4 of the motor may continue to rotate until the energy stored therein is consumed in friction between the surfaces of gear 5 and collar 60, these surfaces, of course, slipping relative to each other and acting as a brake, tending to stop the motor.

Figure 3 is a detailed sectional view showing the manner of attachment of the stationary contacts 38, etc., to the plate 4|. It will be seen that these contacts comprise the head of a screwthreaded member 10 which passes through a non-conducting collar or bushing 12 in the plate and cooperates with a threaded bore in a member '13 back of the plate. By tightening this screw the bushing is rigidly secured in place upon the plate.

Fig. 4 shows in detail the construction of the block 44 carried by the arm 45. This block is of non-conduction material having surfaces adjacent to the plate 4| of V shape, the contact 42 being mounted in a slot at the vertex of the V. Thus the inclined surfaces of the block adjacent to the contact 42 permit the block and the contact to ride smoothly over the rounded surfaces of the stationary contacts with which it cooperates. This block is provided with oppositely extending arbors 13 which pivot in the wings 31 of the arm 45, so that it rocks about these pivots in contact with which it engages is mounted.

The control key assembly Hi of the receiver may be mounted in the receiver in any suitable way as by non-conducting supports attached to members 23 and 24. Preferably it may be arranged on the panel of the receiver beneath the usual dial the keys ll to 22, etc. projecting through the panel. This assembly which may be mountable and demountable as a unit, includes, as seen from the above description, all of the controls necessary for operation of the receiver, including not only the frequency selecting buttons but also the of? button and the additional buttons l9 and 22 for control of the motor and certain receiver circuits in manually tuning of the receiver.

In Figs. 5 and 6 I have shown a modification of the condenser drive in which the ratio of drive by means of the knob automatically shifts after movement of the knob through a predetermined range. In this figure the sun gear in is replaced by a conical surface M on the shaft on which the knob is mounted. The intermediate gear comprises the three balls '55 arranged in a race it which may be made integral with the pulley from which pulley 2 is driven. The outer ball race 18 is provided with a gear 19 which may cooperate with gear 8 of Fig. 1. Race 16 is provided with a cam 80 better shown in Fig. 6 and finger 8! which cooperate with a finger 82 on the shaft of the knob.

As thus arranged during initial movement of the knob the drive is exactly as described in connectionwith Fig. 1. After rotation of the knob in excess of approximately one revolution finger 82 engages cam surface 80 thereby moving the shaft to the right against spring 83 causing balls F5 to move inward sufiiciently to break the drive connection therethrough. Upon further movement of the knob pulley I1 is driven by fingers 8| and 82 at the same speed as the knob.

While I have shown a particular embodiment of my invention, it will, of course, be understood that I do not wish to be limited thereto, since different modifications both in the circuit and in the instrumentality employed may be used without departing from my invention. I contemplate, by the appended claims, to cover any such modifications, as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In a high frequency receiver having a tuning device, the combination of a motor for driving said tuning device, a unitary control key assembly comprising a plurality of keys, certain of said keys corresponding to respective frequencies to which said receiver may be tuned, and other of said keys corresponding to certain other operations to be effected, means automatically responsive to operation of any of said certain keys to energize said motor until the receiver is tuned .to a frequency corresponding to that one of said certain keys operated, and then to deenergize said motor, means responsive to operation of one of said other keys to energize said motor during the entire time during which said key is operated, means responsive to operation of another of said other keys to prevent energization of the motor while said other key is operated and to energize the receiver, and manual means for operating said tuning device when said motor is deenergized.

2. In a high frequency receiver having a tun- I 4 ing device, the combination of a motorfor driving said tuning device, a plurality of keys, certain of said keys corresponding to respective frequencies to which said receiver may be tuned,

andother of said keys corresponding to certain other operations to be efiected, means responsive tooperation of any of said certain keys to energize said motor'until the receiver is tuned to a frequency corresponding to that one of said cer- I gized, said keys being arranged in a unit including means mechanically to retain any of said keys except said one of said other keys in its operated position until another key is operated.

3. In a high frequency receiver having a tuning device, the combination of a motor for driving said tuning device, a plurality ofkeys, cer-' tain of said keys corresponding to respective frequencies to which said receiver'may be tuned, and other of said keys corresponding to certain other'operations to be effected, means responsive to operation of any of said certain keys to energize said motor until the receiver is tuned to a frequency corresponding to that one of said certain keys operated, and to. then deenergize said motor, means responsive to operation of one of said other keys to energize said motor during the entire time when said one other key is operated, means responsive tooperation of another of said keys to prevent energization of said motor while said key is operated and to energize said receiver, manual means for operating said tundevice when said motor is deenergized, means responsive to a third of said other keys to deenergize said motor and receiver, said keys being arranged in a unit including means mechanically to retain any of said keys, except said one-of said other keys, in its operated position until another key is operated.

DONALD R. DE TAR. 

